1) Field of the Invention
The field of the present invention relates to lighting fixtures and systems as may be used in photography, film, television, video, motion picture and other applications.
2) Background
Lighting systems are an integral part of the film, television, video, motion picture, and photography industries. Proper illumination is necessary when filming movies, television shows, or commercials, when shooting video clips, or when taking still photographs, whether such activities are carried out indoors or outdoors. A desired illumination effect may also be ordered for live performances on stage or in any other type of setting.
Various conventional techniques for lighting in the film and television industries, and various illustrations of lighting equipment, are described, for example, in Lighting for Television and Film by Gerald Millerson (3rd ed. 1991), hereby incorporated herein by reference in its entirety, including pages 96-131 and 295-349 thereof, and in Professional Lighting Handbook by Verne Carlson (2nd ed. 1991), also hereby incorporated herein by reference in its entirety, including pages 15-40 thereof.
Fresnel lenses were designed originally to allow for large geometry lensing in lighthouses, well before the advent of the true incandescent light bulb. Fresnel lenses were later used in early theatrical and movie lighting fixtures because they allowed the light to be shaped into beams of smooth light that could project for great distances. Such lighting fixtures are commonly referred to as “Fresnels.”
As stated above, Fresnel fixtures including glass lenses were and are used for film, television, motion picture, and live theatre applications. Typical Fresnel fixtures consist of a metal housing, reflector, light bulb assembly, and Fresnel lens. Fresnels fixtures for theatrical applications are commonly available in lens diameters of 3, 6 or 8 inches with lamps ranging in power from 150 W (typically with a 3-inch Fresnel lens) to 2000 W (with an 8-inch Fresnel lens). In film, television, and motion picture lighting, a much greater range of lens and bulb sizes are typical. For these applications, lenses commonly range in size from 2 to 24 inches, and light bulb power ranges between 200 W and 20,000 W.
Known Fresnel fixtures may have a mechanism for changing the focal distance between the light bulb and the lens. Many Fresnel fixtures allow the light bulb inside the fixture to be moved relative to the lens focal point to increase or decrease the size of the projected light beam. Such adjustment, typically accomplished via a knob on the back of the fixture, varies from a narrowly focused beam (spot) to a wider beam (flood). Fresnel fixtures have been known to produce a beam as narrow as 7° or as wide as 70°.
Fresnel fixtures are useful in the film, motion picture and television industries not only because of their ability to focus a brighter beam than a typical lens, but also because the projected light is of relatively consistent intensity across the entire width of the beam. Fresnel fixtures are also known to produce a very soft-edged beam which makes them suitable for use as a wash light. In still photography, Fresnel fixtures have been used as a highlight, sidelight/backlight or kicker. A frame in front of the lens is often used to hold a gel to tint the light or wire screens to reduce it or frosted plastic to diffuse it. Barn doors are commonly used primarily to control light spillage or to shape the light.
However, this is not to say that existing (and historical) Fresnel lighting fixtures are efficient in any way. These conventional lighting fixtures have drawbacks or limitations which can limit their flexibility and/or effectiveness. Most of the light that is emitted by an omni-directional light bulb inside known Fresnel fixtures actually strikes and is absorbed and wasted by the cylinder shaped housing of these fixtures. A small portion of the light is bounced off a curved mirror in the back of the fixture and a small portion goes directly out the Fresnel lens. This leaves relatively little of the total light generated to be able to exit the Fresnel lens as harnessed light. Incandescent bulbs are very inefficient to start with and by then introducing them into a Fresnel housing their efficiency drops even further. Moreover, the reflector cannot be larger than the lens aperture, and thus all the radiated light that is neither redirected forward by the spherical reflector behind the bulb nor emitted directly through the lens is absorbed by the casing as waste heat. The major drawback of Fresnel fixtures is the enormous amount of heat energy generated by the bulbs and absorbed by the casing.
The light bulbs used in most common Fresnel fixtures used in film, commercial, and photographic settings are either incandescent, tungsten-halogen, xenon, or HID lamp elements. The enormous amount of heat generated by the bulbs affects the manner and duration in which they are used and particularly in their construction. Such lamps emit infrared radiation which would quickly and catastrophically damage a plastic Fresnel lens. Due to the heat generated, care must be taken with regard to the placement of these fixtures, the manner in which they are handled, and the length of time they can be used (excessive heat affects the bulb life). In addition, such fixtures must be constructed so as to withstand the intense heat of this environment. In the case of HMI light based fixtures the bulb emits large amounts of ultraviolet light that is dangerous and needs glass or filtration that blocks the harmful UV rays. As a result, thick, heavy, lenses that are generally made of Pyrex® type glass are used along with heavy gauge metals for the housing and fixture. This means that current Fresnel fixtures are heavy requiring special attention in transport and the way in which they are installed. Due to their weight, the mounting frames used for traditional Fresnel fixtures are often large and ponderous, making them difficult to move around and otherwise work with. A need, therefore, exists for a Fresnel fixture with an efficient, directed light beam which includes active cooling allowing them to be constructed of light weight materials.
Existing Fresnel fixtures do not lend themselves to work with LED illuminators because there is a power density issue when using LEDs. LEDs by their nature are very efficient in making light but they are rather large individually and it is difficult to get enough of them in close proximity to make a pseudo point light source and to be able to remove the heat from them (cool them) properly while they are in such proximity.
LED based Fresnel fixtures are available and used for club lighting or theaters that are very low power, in the 50 watt range. However, they don't have a very tight point source nor do they deal with the power density as they have sealed housings which can only radiate the heat, which limits their ability to transition to the higher power levels required for image capture. These lighting fixtures typically include a variety of colorized LEDs in hues such as red, green, and blue (i.e., an “RGB” combination), and sometimes include other intermixed bright colors as well. These types of fixtures are not well suited for applications requiring more precision lighting, such as film, television, and so on. Among other things, the combination of red, green, and blue (or other) colors creates an uneven lighting effect that would generally be unsuitable for most film, television, video, motion picture or photographic applications. Moreover, most of these LED-based lighting apparatus suffer from a number of other drawbacks, such as requiring expensive and/or inefficient power supplies, incompatibility with traditional AC dimmers, lack of ripple protection (when connected directly to an AC power supply), and lack of thermal (heat) dissipation.
A need, therefore, exists for an LED based Fresnel fixture of over 100 watts that addresses the thermal and power density issues and is suitable for use as a high powered motion picture light. The light should be light weight so that technicians can easily move it, it will preferably be silent so it does not interfere with sound recording; and, it will preferably be efficient in order to justify the transition from incandescent fixtures. In addition, a need exists for such a light which is also dimmable through a great range, focusable from an even wide beam to a tight even spot, and powerful enough to light traditional film, television, video, or movie scenes with the same number of fixtures as is used with incandescent fixtures. The operation and controls should be similar to existing Fresnel fixtures so as to ease the burden on the lighting technicians who are tasked with learning and applying new technology lighting systems.
In remote video capture applications, such as live sporting events, the historical practice was to send a crew, including a director, and technical people including a lighting director and gaffers to the venue along with the broadcast talent to cover an event. These practices incur substantial expense and the lighting traditionally needs large power cables run from large generators stationed outside the venue. It is becoming more common for a broadcaster to send equipment and broadcast talent to a venue which is set up by local technical personnel and it would be desirable to have the lighting equipment operated remotely by the lighting director and technical crew. In the case of live or stored for later broadcast events such as interviews, it has become common practice for the interviewer and interviewee to be in separate studios to conduct the interview rather than one or the other traveling so that the interview can take place face-to-face. Broadcasters have begun and are likely to expand the practice of sending equipment to a location with no crew which can be set up by a local technician or by the interviewee which can be controlled remotely. A need, therefore also exists for a Fresnel fixture which is capable of such remote operation and to operate on standard power from standard outlets.